Sorted !!!!!!!!!!!!!!!!
As I said, I put a straight edge on the caliper mounts on the fork leg
Looks like someone had the problem before ( possibly.......... I have NO idea what they were thinking )
One of the mounting lugs had had about 1.25mm shaved off it.. Impossible to spot with the naked eye
It meant the caliper was twisted
Took the leg out and milled the lugs level
Keeping every digit I have crossed I stuck it back together and Lo ! It worked !!!